This invention relates to an improved prefabricated metal chimney of the type comprised of a plurality of similar chimney sections connectable in an end-to-end relationship.
Such prefabricated chimneys have been widely used in the past because of their inherent advantages over conventional masonry chimneys, including their economy and ease of installation. Despite the relatively high state of development of such chimney structures as exemplified by my previous U.S. Pat. Nos. 4,029,344, 4,029,343, and 3,902,744, certain problems have challenged the increased need for improvements. One problem which arose was in preventing or at least reducing to a minimum the conductivity of heat from the inner pipe to the outer pipe while also maintaining the necessary structural integrity at the ends of each chimney and thus at the joint or connected sections. The use of metal end caps or annular flanges on each section in previous prefabricated chimney devices provided adequate structural integrity but also created a natural path for high heat conductivity and often caused hot spots on the outer surface of an erected chimney. The present invention serves to minimize this problem and provide a more efficient and long-lasting chimney.
Another problem with prefabricated metal chimneys formed with interconnected prefabricated chimney sections was in forming and maintaining an adequate gas seal at the joint connections of such sections. In previous chimney designs the mating end couplings of the chimney sections comprised primarily metal parts that not only conducted a large amount of heat but also tended to create gaps or channels due to normal mismatching tolerances of components which were often increased by their expansion and contraction from heat changes. The escape of gas through such joint gaps or channels could become intolerable for most chimney installations.